Taxes 101: Most common mistakes to avoid

(MoneyWatch) As the United States tax code clocks in at 18,500, pages, it's easy to see how taxpayers can make a mistake or two when filing federal income tax forms. And with over 97,000 full-time employees, you can bet it's not going to go unnoticed.

Here are some of the guiltiest repeat offenders -- steer clear of them and you'll get your refund faster and can avoid having your IRS agent over for a cup of tea.

1. Sign on the dotted line.

Probably the easiest part of preparing your taxes is signing your John Hancock, but it's still one of the most common mistakes year after year. The IRS will not accept your return if you fail to sign and date your income tax form. It delays the process and your refund. Remember also that when filing jointly, both spouses must sign.

2. Check the right box.

Another common mistake is checking the wrong filing status. You have five choices: Single, married filing jointly, married filing separately, head of household and qualifying widower. Taxpayers often incorrectly claim head of household filing status without meeting the requirements. You can qualify for head of household status (and a larger deduction) if you are unmarried at the end of the year, have cared for a closely-related dependent for over half the year and paid more than half the cost of maintaining a home for yourself and your dependent.

3. Be a diligent scribe.

This is another mistake that you can sidestep if you're just a little more careful. The names and Social Security numbers for the taxpayer, the taxpayer's spouse, dependents and children who qualify for the Earned Income Credit or Child Tax Credit must be included on the return exactly as they appear on their Social Security cards.

4. Show them the money.

According to the IRS, taxpayers often make the mistake of failing to report income that's not included on a W-2 or 1099 form, including rental income and self-employment income. If you neglect to report that type of income, it may cost you in the long run: The IRS can assess interest and penalties, not to mention criminal prosecution. Don't risk it.

5. Get the numbers right.

One of the top reasons the IRS adjusts returns is math mistakes, so get out that calculator and start number crunching. It also doesn't hurt to have a second set of eyes check your work. This is another advantage to filing online -- the electronic filing software double-checks your math.

An error-free return means faster processing and a faster refund check for you, so cross your T's and dot your I's and before you put it in the mail, make a copy.